The need to monitor intracranial pressure (ICP) for intensive care situations involving head injury, post-craniotomy hemorrhage, or certain brain disorders has been well established. For example, estimates of head injuries in the U.S. vary from 150,000 to 375,000 annually which are considered moderate or severe and where elevated ICP may occur. Despite the apparent need to monitor ICP, no monitoring system has been adopted for universal use, primarily due to concerns about infection and reliability. LifeSensors, Inc. seeks to test its new design concept for totally implantable ICP monitoring sensor that has minimal risk of infection over extended periods. The proposed design represents a major advance of a telemetric technology developed over 10 years ago at the Johns Hokpkins University School of Medicine. In Phase I, the company plans to complete working drawings for, and to fabricate and test prototype implants in a simulated physiological environment of 0.9% saline at body temperature to demonstrate a major reduction in base line drift, and to eliminate case integrity problems associated with the original design. The design objectives include a base line drift of less than 0.2 mm\H2O (0.015 mmHg) per day and a pressure range of plus and minus 100 mmHg.